One-pot green synthesis of polymeric nanocomposite: Biodegradation studies and application in sorption-degradation of organic pollutants.

The research work proposes the synthesis of a nanocomposite hydrogel which is a dual combination of binary interpenetrating network (BIPN) and bismuth ferrite nanoparticles. BIPN synthesized from binary graft copolymer (BGC) used as starting material. The cross-linked network of BGC is interpenetrating the newly synthesized cross-linked network of poly(acrylic acid) and the product is named as BIPN. Binary graft copolymer had been synthesized from grafting of guggul aqueous extract with copolymeric chains of acrylamide (primary monomer) and acrylic acid (secondary monomer) crosslinked by N,N'-methylene bisacrylamide (MBA). The maximum percentage swelling was evaluated for BGC through optimization of various reaction parameters: amount of water, binary ratio of acrylamide to acrylic acid, concentrations of MBA, ammonium persulphate, pH, temperature and time. Considering pre-optimized parameters for BGC synthesis, BIPN formation required optimization of only acrylic acid. Maximum percentage swelling obtained was 1497.79% and 308.15% for BGC and BIPN, respectively. Maximum percentage biodegradation of 90.64% and 82.38% were calculated for BGC and BIPN, respectively using composting method. Degradation efficiency of brilliant blue (BB) and fuchsin basic (FB) dyes was in the order: Nanocomposite ≫ BIPN > BGC. Maximum percentage degradation observed in case of nanocomposite was 94.1% and 99.3% in sunlight for BB and FB, respectively. The interaction of dyes with the nanocomposite involved mainly ionic interactions. The adsorption models Freundlich and Langmuir were applicable to overall adsorption and degradation process of BB and FB, respectively. Maximum adsorption capacities corresponding to minimum concentration i.e. 10 mg L-1 for BB and FB were calculated as 0.409 mg g-1 and 0.439 mg g-1, respectively. Second order and first order kinetics were found to be suitable for BB and FB adsorption-degradation pathways, respectively. Intraparticle diffusion mechanism was favorable to both dyes and adsorption followed three steps. Gas chromatography coupled with mass spectrometric analysis could give the degraded products which was helpful in drawing degradation pathway. The degradation process involved active radical species (O2-., OH.) and they carry out oxidation-reduction reactions on dyes to give decolorized solution containing mineral ions.

Response surface methodology directed synthesis of luminescent nanocomposite hydrogel for trapping anionic dyes.

The present research work reveals semi-interpenetrating network (semi-IPN) synthesis using response surface methodology-central composite design (RSM-CCD) based optimization. The maximum swelling of 362.11% was obtained with monomer, crosslinker and initiator concentrations 4.39 mol L-1, 1.52 mol L-1 and 4.58 mol L-1, respectively, temperature 70 °C, time 3 h and pH 4.0. The synthesized hydrogel showed 94.16% and 95.62% removal for eosin yellow (EY) and eriochrome black-T (EBT) dyes, respectively. The incorporation of cadmium sulphide nanodots into the hydrogel network enhanced the % dye removal (96.82% EY and 98.73% EBT) along with fluorescent behavior. Various conditions optimized for EY and EBT dye removal with respect to semi-IPN were: 0.4 g adsorbent dose each, dye concentrations 10 mg L-1 and 120 mg L-1, contact time 24 h each, respectively. Adsorption studies followed langmuir theory for both dyes. Second order and first order kinetics along with intraparticle diffusion of dye molecules were favorable to EY and EBT, respectively. Thermodynamic study reveals exothermic nature of adsorption. Recyclability of the adsorbent is superior as tested by desorption-adsorption tests.

Sequestration of Cr (VI) from water using agar-polyvinyl alcohol based cation exchanger.

Present study focuses on the use of a biodegradable and cost-effective cation exchanger for removal of Cr (VI) metal ions from water sources. Semi-IPN was prepared through grafting of acrylamide onto agar-polyvinyl alcohol backbone in presence of boric acid and ammonium per sulphate as crosslinker-initiator system. Graft copolymer was converted to cation exchanger through phosphorylation. Characterization was done using methods such as FTIR, SEM-EDX and XRD. Semi-IPN exhibited higher thermal resistance. The findings revealed that the optimum conditions for Cr (VI) removal are pH = 4.0; contact time (min) = 360; adsorbent dose (mg) = 125 and metal ion concentration(mg/L) =2. The adsorption kinetics of Cr (VI) ions are best fit by the pseudo second order kinetic with 0.99 R2 and Kf (rate constant) was found to be 0.97 thereby supporting the Freundlich isotherm. The adsorption isotherm models used in this study were consistent with the Freundlich model, but the pseudo second order model was the most accurate description of the adsorption kinetics. The present investigation showed an excellent potential with 85 % adsorption capacity for the removal of Cr (VI). Moreover, reusability studies showed that the cation exchanger can be used effectively up to four cycles.

Fabrication of cellulose-collagen based biosorbent as eco-friendly scavengers for uranyl ions.

The aim of the present research is to fabricate a biosorbent using agricultural waste for removal of uranium from contaminated water i.e. "waste to wealth" approach. Cellulose extracted from wheat straw was mercerized and a novel semi-interpenetrating polymer network (semi-IPN) was fabricated through graft copolymerization of polyvinyl alcohol onto hybrid mercerized cellulose + collagen backbone. Response surface methodology was used for optimization of different reaction parameters as a function of % grafting (195.1 %) was carried out. Semi-IPN was found to possess higher thermal stability. Adsorption results revealed that the optimum parameters for the elimination of uranium using semi-IPN were: adsorbent dose = 0.15 g, pH = 6.0, contact time = 120 min and initial U (VI) concentration = 100 µg/L. The pseudo-second-order kinetic model gave the best description of the adsorption equilibrium data as the calculated qe value is nearest to the experimental qe for the different initial U(VI) concentrations. Adsorption experiments followed Langmuir isotherm with R2 = 0.999. Furthermore, recyclability and reusability studies showed that the adsorption efficiency of semi-IPN was 82 % after 5 cycles indicating the superior recycling execution of fabricated biosorbent. Thus, the fabricated ecofriendly device can be used effectively for the removal of uranium from contaminated wastewater sources.

Design and evaluation of fluorescent chitosan-starch hydrogel for drug delivery and sensing applications.

Composite bio-based hydrogels have been obtaining a significant attention in recent years as one of the most promising drug delivery systems. In the present study, the preparation of composite chitosan-starch hydrogel using maleic acid as a cross-linker was optimized with the help of response surface methodology. The synthesized hydrogel was fluorescent owing to clustering of large number of functional groups. Different analytical techniques, including XRD, FTIR, SEM, XPS, fluorescence and BET were utilized to characterize the prepared hydrogel. XRD analysis confirmed the formation of non-crystalline hydrogel with random arrangement of macromolecular chains. The composite hydrogel exhibited good swelling percentage with pH sensitivity, hemocompatibility and degradability. BET analysis confirmed that the variation in concentration of crosslinker significantly influences the pore volume of the hydrogel. The synthesized composite chitosan-starch hydrogel was utilized as a prospective candidate for controlling drug release. Cefixime as a model drug was loaded onto the synthesized hydrogel utilizing the swelling diffusion method. SEM micrographs showed uniform distribution of drug molecules in the drug loaded hydrogel. In vitro drug release experiments indicated the swelling dependent drug release behaviour of chitosan-starch hydrogel with higher drug release at pH 7.4 (93.08 %) compared to pH 1.2 (67.85 %). The composite chitosan-starch hydrogel was able to prolong and control the drug release up to 12 h. The drug release from the hydrogel followed Korsmeyer-Peppas and Makoid-Banakar model with Fickian diffusion mechanism. Further, the composite hydrogel displayed excitation dependent fluorescence emission with most intense blue emission band at 425 nm with an excitation wavelength of 350 nm. The inclusion of cefixime drug in the hydrogel matrix significantly reduced the fluorescence intensity; the decrease was linearly correlated to the concentration of the drug. Moreover, the fluorescence emission the chitosan-starch hydrogel was found to be dependent upon pH. The synthesized hydrogel is expected to be a potential candidate for controlled drug release as well as for fluorescent sensing applications.

Synthesis of dextrin-polyacrylamide and boric acid based tough and transparent, self-healing, superabsorbent film.

Stretchabiliy, transparency and self-healing ability of bio-based materials are some of the important features for their utilization in the biomedical field. Recently, robust self-healing super porous materials possessing multifunctional nature have raised enormous interest among the researchers in order to design different materials which can be used in industrial, biomedical and pharmaceutical fields. Herein, a novel self-healing, stretchable and transparent superabsorbent film based on Dextrin-polyacrylamide and Boric Acid (DEX-cl-polyAAm) was synthesized using a free radical reaction mechanism. In distilled water, the maximum water absorptivity of the synthesized film was reported to be 3156% after the optimization of various reaction parameters. The film was also found to show structural integrity in urea solution, phosphate buffer and solutions of different pH. Lastly, the viscoelastic and self-healing analysis of the film suggested its utility towards biomedical field.

Synergic effect of Guggul gum based hydrogel nanocomposite: An approach towards adsorption-photocatalysis of Magenta-O.

The article is related to sunlight and UV-visible mineralization of harmful magenta-O (FB) dye. The nanocomposite used is a cross linked network of acrylic acid synthesized inside poly(acrylamide) grafted Guggul gum in the presence of UV-visible respondent bismuth ferrite nanoparticles. The synthesis of poly(acrylamide) grafted Guggul gum (Sample I) and synthesizing a crosslinked network inside it (Sample II) involved a two-step synthesis for optimizing various reaction parameters. The maximum % water uptake obtained for polymeric samples I and II was calculated as 1227.78% and 387.97%, respectively. Average particle size of bismuth ferrite nanoparticles was 47.34 nm. The nanocomposite could maximum uptake-mineralize FB dye as 97.3% and 98.8% under sunlight and photochemical reactor, respectively for 500 mg nanocomposite dose in 10 mg/L concentrated FB solution. Dye uptake occurs through ionic interactions. However, mineralization is a consequence of advanced oxidation process involving free radical species (OH and O2-.). The overall process of uptake-mineralization resembled second order kinetics and Langmuir theorem (monolayer adsorption). Intraparticle diffusion model gave an idea about the multistep (three steps) process of adsorption. Physico-chemical properties of FB dye got changed after mineralization except for the pH. The maximum uptake-mineralization was observed to be 76.2% after consecutive reuse of the nanocomposite hydrogel for five cycles.

Chemically modified chitosan­sodium alginate as chemo-sensor adsorbent for the detection of picric acid and removal of biebrich scarlet.

We report here on the green synthesis method of hydrogel nanocomposite (Na-Ala/Chit-cl-polyAAm/CQDs) incorporated with carbon quantum dots for picric acid sensing and biebrich scharlet dye removal from industrial waste water. The nanocomposite precursor was derived from chitosan­sodium alginate hybrid backbone and acrylamide monomer through the formation of semi-IPN matrix (Na-Ala/Chit-cl-polyAAm). The swelling percentage of semi-IPN can be controlled through process parameters such as reaction time, temperature, pH, water volume, acrylamide, N,N'-methylenebisacrylamide and ammonium persulphate concentrations. Hydrogel nanocomposite displayed 99% quenching efficiency for the selective detection of picric acid and 96% dye removal efficiency was found to be observed for the removal of biebrich scarlet dye. The sorption was found to be favorable though Freundlich and Temkin adsorption isotherms along with the 2nd order kinetics. The devices were found to be recyclable and reusable up to six consecutive cycles indicating their applicability in textile industries for the treatment of effluents.

Study of a cross-linked hydrogel of Karaya gum and Starch as a controlled drug delivery system.

A cross-linked hydrogel was synthesized using a hybrid backbone of karaya gum starch and grafted with polyacrylic acid. It showed a maximum swelling ratio (SR) of 30.5 g/g at pH 10 and was explored as an oral drug delivery carrier using paracetamol and aspirin as model drugs. In vitro release experiments revealed that maximum drug release at pH 7.4 in comparison to pH 1.2 (simulated intestinal vs gastric fluid) and neutral medium. The release profiles of these drugs showed no initial burst. It also showed good hemocompatibilty and non-cytotoxicity for its employment as a site specific drug delivery agent.

RSM-CCD optimized sodium alginate/gelatin based ZnS-nanocomposite hydrogel for the effective removal of biebrich scarlet and crystal violet dyes.

The present work represents RSM-CCD (Response Surface Methodology integrated Central composite Design) optimized synthesis scheme of semi-IPN (semi interpenetrating network) NaAla-Gel-cl-polyAAm and ZnS nanocomposite adsorbent NaAla-Gel-cl-polyAAm/ZnS. Under optimized reaction parameters semi-IPN NaAla-Gel-cl-polyAAm showed maximum swelling percentage of 3191.73%. Maximum dye removal percentage (97.37%) was observed with ZnS nanocomposite for the removal of biebrich scarlet. The adsorption isotherm data indicated that Langmuir and Freundlich adsorption isotherm fitted well for biebrich scarlet (R2 = 0.964) and crystal violet (R2 = 0.960), respectively. ΔG°, ΔH° and ΔS° values indicated the thermodynamic feasibility of the reaction. Excellent recyclability and reusability of the adsorbent materials suggested their applicability towards textile industry and water purification purpose.

Selective removal of cationic dyes using response surface methodology optimized gum acacia-sodium alginate blended superadsorbent.

Gum acacia and sodium alginate were blended to synthesize highly efficient superadsorbent formed by grafting of poly(acrylic acid) (AA) used as monomer onto the hybrid of gum acacia and sodium alginate and the polymeric chains were crosslinked through N,N'-methylene bisacrylamide (MBA). The overall reaction followed free radical polymerization with ammonium persulphate (APS) used as initiator. Response surface methodology integrated with central composite design (RSM-CCD) could synthesize semi-Interpenetrating network (semi-IPN) having maximum swelling capacity of 1749.2% at MBA, APS and AA concentrations of 0.89 × 10-2 mol L-1, 3.29 × 10-2 mol L-1 and 1.46 mol L-1, respectively using 15 mL water at 70 °C for 2.5 h. The synthesized sample was found to be selective for removal of cationic dyes upto 97.49%, 95.39% and 94.56% for auramine-O (AO), malachite green (MG) and crystal violet (CV), respectively. Adsorption capacities at equilibrium were calculated experimentally as 2.01 mg g-1, 3.06 mg g-1 and 7.55 mg g-1 for AO, MG and CV, respectively. These dyes could be desorbed with 0.1 N HCl for the recyclization of semi-IPN. Adsorption mechanism involved monolayer formation with three step process of adsorption and followed first order kinetics. Exothermic nature of adsorption was revealed by thermodynamic studies.

Synthesis of a biodegradable interpenetrating polymer network of Av-cl-poly(AA-ipn-AAm) for malachite green dye removal: kinetics and thermodynamic studies.

This paper deals with the synthesis of a biodegradable interpenetrating polymer network (IPN) from the natural polysaccharide aloe vera (Av), acrylamide (AAm) and acrylic acid (AA), and its evaluation as a dye removal device. In the synthesis of Av-cl-poly(AA-ipn-AAm), ammonium persulfate (APS) was used as an initiator, N,N'-methylene bisacrylamide (MBA) as a cross-linker, AA and AAm as primary and secondary monomers, respectively. Soil burial and composting methods were used to study the biodegradability of the synthesized IPN and the results showed 94% degradation within 70 days using the composting method and 86% degradation within 77 days using the soil burial method. Biodegradation was confirmed by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) techniques. The synthesized IPN was used as a device for the removal of malachite green (MG) dye from aqueous solution. The maximum MG removal capacity of the synthesized IPN was found to be 97.3% under the optimal conditions (i.e. time = 180 min., pH = 4.5, adsorbent dose = 5 g L-1). The adsorption kinetics of malachite green molecules onto synthesized IPN was studied and compared using pseudo-first-order and pseudo-second-order models and we found that the adsorption process is better represented by the pseudo-second-order model. The different adsorption isotherm models like Langmuir, Freundlich, Dubinin-Radushkevich, Temkin, Redlich-Peterson and Sips isotherms were studied. The best-fitting isotherm model for the present experiment is the Langmuir model.

A Novel approach for the morphology controlled synthesis of rod-shaped nano-hydroxyapatite using semi-IPN and IPN as a template.

Present work offers use of semi-interpenetrating network (semi-IPN) and interpenetrating network (IPN) as the template for the synthesis of nano-hydroxyapatites. Semi-IPN and IPN of agar-gelatin were prepared and successfully used to synthesize nano-hydroxyapatite. Graft copolymerization technique was used to alter the properties of the hybrid backbone using ammonium persulphate as an initiator and N,N'methylene-bisacrylamide (MBA) as a crosslinker. The first step was to synthesize cross-linked semi-IPN of agar-gelatin blend which was converted to a cross-linked interpenetrating polymer. Semi-IPN and IPN showed 4786% and 4896% swelling, respectively. In the second step in situ synthesis of rod-shaped nano-hydroxyapatites was carried out. Ca/P ratio for hydroxyapatite formed was found to be 1.67 for semi-IPN and 1.63 for IPN with the particle size of 50-100nm (length) and 6-15nm (diameter). These results were than compared with the literature findings of synthesizing n-HA (nano-hydroxyapatite) without using templates and results were better for n-HA synthesized using templates. Thus, the use of semi-IPN and IPN for the controlled growth of rod-shaped nano-hydroxyapatite was a novel approach.

Synthesis and flocculation properties of gum ghatti and poly(acrylamide-co-acrylonitrile) based biodegradable hydrogels.

This article reports the development of biodegradable flocculants based on graft co-polymers of gum ghatti (Gg) and a mixture of acrylamide and acrylonitrile co-monomers (AAm-co-AN). The hydrogel polymer exhibited an excellent swelling capacity of 921% in neutral medium at 60°C. The polymer was used to remove saline water from various petroleum fraction-saline water emulsions. The flocculation characteristics of the hydrogel polymer were studied in turbid kaolin solution as a function of the amount of polymer and the solution temperature and pH. Biodegradation studies of hydrogel polymer were conducted using the soil composting method, and the degradation process was constantly monitored using scanning electron microscopy and Fourier transform infrared spectroscopy techniques. The results demonstrated an 89.47% degradation of the polymer after 60 days. Finally, the hydrogel polymer adsorbed 98% of cationic dyes from the aqueous solutions.